Hi,
I want to import many requests tickets (lets say 12k for example) to a single JSM project.
I tried using External system import with my .csv file that contains maximum allowed limit of 6k tickets - at the end of the process I selected a new project name and key and after some time, everything went well - I can find my 6k tickets into this newly created JSM project.
The problem I have is that when I try to import the rest (another 6k) tickets into the same JSM project - I get the warning that project already exist. It seems that with External system import tool it is not possible to add tickets from csv file into the existing project. 
I also tried tried using a configuration import file where in the projectData section i set "isExistingProject": true but this does not make the new project creation required at the end of the import.
Importing tickets from the previously created space via csv is not a option since there is a limit of only 250 tickets per csv file.
Thanks for help